Automatic profiling machine

Abstract

A model and a workpiece are rotated synchronously, and a stylus is disposed for relative movement toward or away from the model in a direction perpendicular to the axis of rotation thereof for contact therewith. The amount of displacement of the stylus from its neutral point which occurs while it contacts the model is detected by a tracer head and is divided into a pair of components lying in a plane perpendicular to the axis of rotation of the model which are along the direction of said relative movement and along a direction orthogonal thereto. The distance between the center of rotation of the model and the center of the stylus is also detected, and is utilized together with the two orthogonal components of the displacement, the radius of the stylus, a reference displacement of the stylus as well as an established speed therefor in order to control the speed of rotation of the model and the speed of said relative movement between the stylus and the model so that the speed with which the point of contact between the stylus and the model moves along the contour of the model becomes equal to a preselected value. A workpiece and a tool therefor are disposed in a similar relationship as the relationship between the model and the stylus, and are driven in synchronism with the model and the stylus for profiling the workpiece. Where the tool contacts the workpiece over a certain width as with an abrasive belt, the contact segment of the stylus is angularly moved so as to follow the curved surface of the model, thereby detecting an angle of skew of the curved surface so that the angle of skew of the tool coincides with the detected angle.

We claim: 
     
       1. An automatic profiling machine comprising means for rotating a model, means for rotating a workpiece in synchronism with the rotation of the model, a stylus capable of relative movement with respect to the model in a direction perpendicular to the axis of rotation of the model and adapted for contact therewith, means for detecting a displacement of the stylus from its neutral point as it contacts the model, means for detecting a distance between the center of the stylus and the center of rotation of the model, means for controlling the rotational speed of the model and the speed of relative movement between the model and the stylus in accordance with the detected values of said displacement and distance so that the point of contact between the stylus and the model moves along the contour of the model with a given speed, a tool for machining the workpiece, the tool being disposed in the same positional relationship as that between the model and the stylus, means for causing a relative movement between the tool and the workpiece in a manner similar to the relative movement between the stylus and the model, means for rotatably holding a contact segment of the stylus against the model so that the segment is in exact conformity to the surface thereof, means for detecting a rotation of the contact segment, and means for causing a skew of the tool in accordance with the detection of the rotation. 
     
     
       2. An automatic profiling machine according to claim 1 in which the tool is an abrasive belt. 
     
     
       3. An automatic profiling machine according to claim 1 in which the speed control means comprises means for deriving from a pair of components ε cos θ and ε sin θ of the displacement of the stylus in a pair of orthogonal directions in a plane which is perpendicular to the axis of rotation of the model and from a distance R between the center of rotation of the model and the center of the stylus a rotational speed control signal ##EQU13## and means for deriving a control signal for the speed of relative movement ##EQU14## wherein V= V O  + r(dθ/dt), V O  is a given speed along the contour of the model, r the radius of the stylus, ε O  a reference displacement of the stylus and K a constant. 
     
     
       4. An automatic profiling machine according to claim 3, further including adjusting means for modifying the value of r except for that appearing in the term r(dθ/dt) to a smaller value than its actual value, and means for multiplying the term (dθ/dt) by a factor which is less than unity. 
     
     
       5. An automatic profiling machine according to claim 1 in which the speed control means comprises for deriving from a pair of components ε cos θ and ε sin θ of a displacement of the stylus in a pair of orthogonal directions in a plane which is perpendicular to the axis of rotation of the model and from a distance r between the center of rotation of the model and the center of the stylus, a rotational speed control signal ##EQU15## and means for deriving a control signal for the speed of the relative movement ##EQU16## wherein V= V O  + k 2  r(dθ/dt), V O  is a given value along the contour of the model, r the radius of the stylus, ε O  a reference displacement of the stylus, and K and k 2  constants. 
     
     
       6. An automatic profiling machine according to claim 1, further including means for moving the model and the stylus according to each other in a direction along the axis of rotation of the model, means for moving the workpiece and the tool relative to each other in a direction along the axis of rotation of the workpiece in a similar manner as the axial relative movement between the model and the stylus, and means for controlling both speeds of axial relative movement in inverse proportion to a period of rotation of the model. 
     
     
       7. An automatic profiling apparatus comprising: means for rotating a model;   means for rotating a workpiece in synchronism with the rotation of the model;   a stylus capable of relative movement with respect to the model in a direction perpendicular to the axis of rotation of the model and adapted for contact therewith;   means for detecting, as an electrical signal, a displacement, ε-ε O , of the stylus from its neutral point in a plane perpendicular to the axis of rotation of the model as the stylus contacts the model;   means for detecting a distance, R, between the center of the stylus and the center of rotation of the model, in the form of an electrical signal;   means for calculating a changing ratio in time, dθ/dt, of an angle θ between a line joining the center of the stylus with the center of rotation of the model and a normal to the point of contact of the stylus with the model, based on the electrical signal of the displacement ε-ε O  obtained by the displacement detecting means;   means for deriving a signal for controlling the rotational speed of the model, from the electrical signals respectively indicative of ε-ε O , R and dθ/dt;   means for deriving a signal for controlling the relative movement between the model and the stylus, from the electrical signals respectively indicative of ε-ε O , R and dθ/dt;   means for detecting the rotational speed of the model;   means for detecting the speed of the relative movement between the model and the stylus;   a servo loop for controlling the model rotating means by the rotational speed detecting signal and the rotational speed control signal so that the former signal may be coincident with the latter;   a servo loop for controlling the speed of the relative movement between the stylus and the model by the relative movement speed detecting signal and the relative movement speed control signal so that the former signal may be coincident with the latter, the speed at which the point of contact between the stylus and the model moves along the contour of the model being maintained at a constant value by the control of the both servo loops;   a tool disposed in a positional relationship to the workpiece on a manner similar to the positional relationship between the stylus and the model for machining the workpiece; and   means for causing a relative movement between the tool and the workpiece in a manner similar to the relative movement between the stylus and the model.   
     
     
       8. The automatic profiling apparatus of claim 7 further including means for holding a contact segment of the stylus against the model to be rotatable about an axis perpendicular to the axis of rotation of the model so that the contact segment is in exact conformity to the surface of the model, means for detecting the state of rotation of the contact segment, and means for causing a skew of the tool relative to the axis of rotation of the workpiece in accordance with the detection of the state of rotation of the segment. 
     
     
       9. The automatic profiling apparatus of claim 8 wherein the tool is an abrasive belt. 
     
     
       10. The automatic profiling apparatus of claim 7 wherein the rotational speed control signal deriving means is a means for obtaining ##EQU17## from two components ε cos θ and ε sin θ of the displacement of the stylus in a direction of the relative movement between the stylus and the model in a plane perpendicular to the axis of rotation of the model and in a direction perpendicular to the direction of the relative movement, the electrical signal of the distance R and the electrical signal of the changing ratio dθ/dt, and the relative movement speed control signal deriving means is a means for obtaining ##EQU18## from the components ε cos θ and ε sin θ, the signal of the distance R and the signal of the changing ratio dθ/dt, V= V O  + r(dθ/dt), V O  being a given speed along the contour of the model, r the radius of the stylus, ε O  a reference displacement of the stylus, and K a constant. 
     
     
       11. The automatic profiling apparatus of claim 10, further including adjusting means for modifying the value of r except for that appearing in the term r(dθ/dt) to a smaller value than its actual value, and means for multiplying the term dθ/dt by a factor which is less than unity. 
     
     
       12. The automatic profiling apparatus of claim 7 wherein the rotational speed control signal deriving means is a means for obtaining ##EQU19## from two components ε cos θ and ε sin θ of the displacement of the stylus in a direction of the relative movement between the stylus and the model in a plane perpendicular to the axis of rotation of the model and in a direction perpendicular to the direction of the relative movement, the electrical signal of the distance R and the electrical signal of the changing ratio dθ/dt, and the movement speed control signal deriving means is a means for obtaining   Vx = V{sinθ+K(ε-ε.sub.O)cosθ }     from the components ε cos θ, ε sin θ, the signal of the distance R and the signal of the changing ratio dθ/dt, V= V O  + K 2  .r(dθ/dt), V O  being a given speed along the contour of the model, r the radius of the stylus, ε O  a reference displacement of the stylus and K and K 2  constants.   
     
     
       13. The automatic profiling apparatus of claim 7 further including means for moving the model and the stylus relative to each other in a direction along the axis of rotation of the model, and means for moving the workpiece and the tool relative to each other in a direction along the axis of rotation of the workpiece in a similar manner to the axial relative movement between the model and stylus. 
     
     
       14. The automatic profiling apparatus of claim 13 further including means for controlling both of the speeds of axial relative movement in inverse proportion to a period of rotation of the model.